[maybeok]

For the DB use postgres to save licensing costs. I would be more adamant about the DB decision than the language. It's nice to be able to deploy unlimited postgres DBs on as many servers as you need without breaking the bank.

In the future you may have ancillary services/apps better off using a separate DB for performance. DB licensing costs will influence your design decisions so remove those costs from the equation.

C# is fine though (even on linux) and will give you reasonable performance, likely better than node.js is most cases.

[GFischer]

To be fair, they could apply to BizSpark and the licensing and hosting costs would be moot for 3 years (and it has lots of great benefits):

https://www.microsoft.com/bizspark

Btw, you can host Node.js apps on Azure if you like (I do), and a Linux stack if that's your thing, so it makes sense to apply to BizSpark even if you're not going the C# route.